页岩气田某集气管线焊缝失效原因分析

Failure analysis of gas gathering pipeline welds in shale gas field

目的明确四川某现役页岩气平台集气管线环焊缝泄漏失效的原因。方法通过宏观形貌分析、无损检测、理化性能测试、金相组织分析和焊缝区域微观分析等方法对焊缝进行失效分析。结果管段样品存在不同程度的焊接余高超标、咬边、焊瘤和错边等现象,使其焊缝区域可能存在应力集中的问题;焊接施工前因天气原因导致管道内壁和坡口区域产生大量含水铁锈,焊接过程中这些铁锈可能进入熔敷金属中造成焊缝区域扩散氢含量过高,并导致焊接接头处氢致开裂敏感性增加。结论在管道焊缝受外界环境作用下而产生应力集中与焊缝区域中氢含量超高等因素的共同影响下,焊缝区域发生氢致开裂,大量微裂纹断续合并形成宏观开裂失效。

Objective Clarify the reasons for the leakage and failure of the gas-gathering pipeline welds on an active shale gas platform in Sichuan.Methods Failure analysis of welds is conducted based on macroscopic morphology analysis,non-destructive testing,physical and chemical performance testing,metallographic structure analysis,and microscopic analysis of the weld area.Results There are many defects in the pipe section specimen,such as excessive welding reinforcement,undercut,overlap,and misalignment,which may lead to stress concentration in the welding area;prior to welding construction,due to weather conditions,a large amount of water containing rusts are easily generated on the inner wall and groove area of the pipeline.During welding,these rusts may enter the deposited metal,causing excessive hydrogen content in the weld zone diffusion and increasing sensitivity to hydrogeninduced cracking at the welded joint.Conclusions Hydrogen induced cracking(HIC)in the weld seam area occurs under the combined influence of the external environment,stress concentration of pipeline welds,and excessive hydrogen content in the weld area,a large number of HIC microcracks intermittently merging to form macroscopic cracking failure.